The present invention relates to a circuit breaker, such as circuit breaker for wiring, earth leakage breaker or the like, and specifically relates to an electromagnetic repulsion type arc quenching device of a circuit breaker.
The so-called de-ion type arc quenching device shown in FIG. 6 is well known as this sort of an arc quenching device for a circuit breaker. This arc quenching device 1 is structured such that magnetic plates 3 with V-shaped cut-offs or notches for allowing a moving contact member 2 to pass are piled up with adequate spacings and are supported with side walls 4 made of an insulation material. The magnetic plates 3 are fixed to the side walls by adhering or press-fixing.
FIG. 7 shows a longitudinal sectional view of a circuit breaker with the de-ion type arc quenching device in a power supply side. A stationary contact member 6 formed integrally with a power supply terminal 5 is bent back into a U-shape along a moving contact member 2, and a stationary contact 8 contacting a moving contact 7 of the moving contact member 2 is attached at an end of a bent back part 6a of the stationary contact member 6. And, an arc horn 9, which leads an arc caused between the moving contact 7 and the stationary contact 8 toward the arc quenching device 1, is attached to the stationary contact member 6.
As is well known, a current flowing through the bent back part 6a of the stationary contact member 6 and a current flowing through the moving contact member 2 positioned parallel to the bent back part flow in opposite directions as shown by arrows A in the figure. Therefore, owing to an electromagnetic repulsion force acting between these currents, the moving contact member 2 is sprung up by this electromagnetic repulsion force if a large current, such as a short-circuit current etc., flows. As a result, the moving contact member 2 is driven by a current limiting mechanism 10 and is quickly opened to the position shown by a chain line in the figure without awaiting the operation of a switching mechanism 11. Further, the arc 12 caused between the moving contact 7 and the stationary contact 8 receives the force toward the direction shown by an arrow B by a magnetic field of the current flowing through the bent back part 6a, and is urged deeply into the arc quenching device 1. This arc 12 is elongated in the arc quenching device 1 to raise the arc voltage, and then, the arc is quenched in a short time.
However, this sort of arc quenching device requires a complicated work for fixing many magnetic plates 3 to the side walls 4 and high cost. In addition, there are problems such that when a large current is cut or broken, the surface of the magnetic plate is melted by arc heat, and metal particles thus formed are attached to the surface of the contacts resulting in abnormal temperature rise, or attached to the switching mechanism resulting in impeding normal operation of the switching mechanism.
On the other hand, in the electromagnetic repulsion type circuit breakers shown in FIG. 7, a magnetic driving core of a U-shape is attached crosswise to the bent back Dart 6a of the stationary contact member, and magnetic flux generated by the current flowing through the bent back part is concentrated on the magnetic driving core so as to enhance action of magnetic field to an arc. This circuit breaker is disclosed in Japanese Laid Open Patent Publication (Kokai) No. 02-132716 and so on. In this circuit breaker of the prior art, the magnetic driving core is attached to the stationary contact member separately from the arc quenching device to thereby complicate the structure.
In Japanese Laid Open Patent Publication (Kokai) No. 62-93829, an arc quenching device includes a U-shape magnetic element having gas exhaust holes at a back plate and an insulating material for covering the magnetic element, which is formed separately from electric contacts. Also, in Japanese Laid Open Patent Publication (Kokai) No. 63-133422, an arc quenching device includes a U-shape magnetic element, and an insulating material for covering the magnetic element and forming heat decomposing gas by the arc. A fixed contact is formed separately from the magnetic element, but may extend to the magnetic element to form a separation plate for the magnetic element.
In viewing the foregoing, an object of the present invention is to provide an arc quenching device of a circuit breaker, which has no piled magnetic plates, and therefore, is simple in manufacturing and causes little damages by arc heat.
Another object of the present invention is to provide an arc quenching device of a circuit breaker, which simplifies its structure by integrally providing an arc quenching device with a magnetic driving core and an arc horn.